Private eye Bo Dietl has a new best friend: Gov. Paterson, who came to his Christmas party last week in the private room at Sparks Steak House, where business reporter Charlie Gasparino, former Jets linebacker Greg Buttle and Judge Edwin Torres were spreading yuletide cheer. Two days later, when Paterson called Dietl to thank him, Bo invited him for Christmas Eve at Rao’s in East Harlem. Paterson came with daughter Ashley, 21. “The governor is one cool dude,” Dietl told us yesterday. “He’s a lot sharper than people think. He’s got himself geared up. He’s focusing. Beware, Andrew.”